New ATLAS publication
June 30, 2021Collider Physics Group
“Measurement of the tttt production cross section in pp collisions at sqrt(s)=13 TeV with the ATLAS detector ” has been submitted to JHEP. Members of the IFAE-ATLAS team (Aurelio Juste, Nicola Orlando, and Anil Sonay) have played a leading role in this publication, from designing the analysis strategy to the final multivariate technique and statistical analysis employed.
This paper presents a measurement of the four-top-quark production cross section in final states with a single lepton or an opposite-sign lepton pair in association with multiple jets using the full Run 2 dataset collected with the ATLAS detector. With four top quarks produced per event, this is a very rare Standard Model process with a predicted cross section of only 12 fb, and thus is very sensitive to beyond-the-SM (BSM) contributions. A sophisticated event categorization and multivariate technique is used to discriminate signal from background events. The result of this analysis is combined with a previous measurement in multilepton final states. The combined cross section is measured to be a factor of two higher than the SM prediction, although compatible with it within 2.0 standard deviations. The corresponding observed (expected) signal significance is .7 (2.6) standard deviations over the background-only prediction.
The IFAE team is currently working on an improved analysis targeting BSM production of four-top-quark events. Stay tuned!
More information on the ATLAS Physics Briefing
New positions in the IFAE Organization
January 16, 2023
Mario Martinez, ICREA professor at IFAE and head of the Gravitational Waves Group, is the new Director of the Experimental Division and takes on the role of IFAE Deputy Director. Martine Bosman, retiring Director of the Experimental Division, assumes the status of IFAE Emeritus.